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Dirty bit for a page in a page table
(a) helps avoid unnecessary writes on a paging device
(b) helps maintain LRU information
(c) allows only read on a page
(d) None of the above



Amit Pal @amitpal101
25 Sep 2016 11:36 pm

Use of dirty bit : It is used to avoid unnecesary write to secondary memory . when any page fault occours MMU tries to put required page in page table and swap one page to memory . here it check if dirty bit is enabled means page is modified so need ro write back to storage otherwise it simply replace that page with required page without any write back operations . so it saves time  to serivce the page fault . 

Ans (a) helps avoid unnecessary writes on a paging device